Modem electronic assemblies often have housings that enclose and support circuit boards, such as printed wiring assemblies (PWAs) in parallel or orthogonal relationships to each other. These assemblies generally can include multiple daughterboards with connectors that mate with connectors on a common motherboard. The daughterboards and motherboard are attached to and are supported by a common housing, or chassis. A daughterboard generally can include a printed wiring board (PWB) having one or more parallel patterned surfaces and/or buried conductive layers separated by insulating layers. The conductive layers are generally parallel to a major surface of the PWB.
A PWA can have components, such as heat sinks and subassemblies of various types mounted and connected to the patterned conductive paths and ground planes of an associated PWB. The PWAs and other circuit boards are often manufactured according to a particular standard that specifies physical and electrical parameters. One example of a well-known PWA standard is the Peripheral Component Interface (PCI) standard. As a result, the daughterboards and connectors thereof are electrically and mechanically compatible with the motherboard and supporting chassis to enable such daughterboards to be exchangeable with other daughterboards and to enable different manufacturers to provide the PWAs.
Electronic assemblies used in demanding environments such as for military, space and aerospace applications generally have stringent size, weight, shock, vibration and temperature cycling specifications. These specifications are set forth such that the electronic assemblies have a greater capability to survive extreme mechanical and thermal stress while maintaining optimal operational capability throughout the life cycle of the assembly. Mechanical forces, such as vibration and mechanical shock resulting from various sources, are often directly transferred to the PWAs or other circuit boards through the structure of the electronics assembly. Thus, it is desirable for PWA rigidity and clearance characteristics to prevent the components or other structures on adjacent PWAs from deflecting into each other or “rattling,” which can cause undesirable secondary shock and vibration stresses.
In the past, a PWA has been typically supported in a housing or chassis only along two opposite edges of the associated PWB by edge supports that also act as card or board guides to facilitate guided insertion and extraction of the PWA and facilitate connector alignment. As a result, the central portions of such a prior art PWA are self-supporting. Relatively large PWAs have large surface areas and mass that are stiffened for suitability in a particular application such as space applications. For instance, increasing the thickness of the PWB and/or adding rib or frame supports to one or both major surfaces of the PWB has accomplished this stiffening in the past. These solutions can however result in an undesirable increase in size, weight, volume and cost of the assembly. Such metal rib and/or frame supports can also provide additional thermal conduction cooling paths between components and other structures mounted on the PWB and the board edges supported by the chassis. However the thermal resistance from centrally located components to such thermal paths at the supported edges of the PWBs of some prior art assemblies can be undesirably large resulting in the components thereof tending to have undesirably increased operating temperatures.
In view of the foregoing, it should be appreciated that there is a need to provide an apparatus for providing increased ruggedized mechanical support of circuit boards such as PWAs within a chassis. In addition, it is desirable for such apparatus to provide a minimum increase in volume, weight and cost. Moreover, it is desired that such apparatus provide improved or additional thermal paths between the circuit boards and the chassis. Furthermore, such apparatus is desirably compatible with industry standards relating to such assemblies. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention, brief summary of the invention, abstract, and appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background of the invention.